Asphalt roofing shingles are based on an interior web or carrier commonly formed as a glass fiber mat in a wet process. Shingle manufacturing consists of running a continuous wet process glass fiber mat in a bath of molten asphalt to cause a coating on both sides of the mat, as well as filling the interstices between the individual glass fibers.
Wet process glass fiber mats are conventionally made from glass fibers held together by a binder comprising a thermoset polymer system. Typically, a binder is applied in a liquid form and dispersed onto the glass fibers through an applicator such as a curtain coater. Conventional wet processes strive to produce a uniform coating of binder on the glass fibers. After the binder and glass fibers have been dried and cured in an oven, the glass fiber mat is gauged and cut as desired.
Typically, cuts are made in a glass fiber mat along the longitudinal length of the mat to produce several mats of a desired width. Each cutting operation produces side edges for each of the narrower mats. The cutting operation may expose or produce weaker areas in the mat along the side edges. The weakened mat edge can break during a coating process or result in a shingle having a weakened edge, i.e., an edge prone to tearing or breaking during handling or installation. Conventional techniques for reinforcing such edges include the addition of a yarn or tape to the desired portion of the glass fiber mat. The addition of such materials can increase the cost of manufacture of glass fiber mats.
It is desirable to improve the performance of glass fiber mats and prevent cut edges from exposing areas prone to breaking or tearing. Furthermore, it is desirable to produce glass fiber mats which produce shingles having increased tear strength and pliability.